1. Field of the Invention
This invention relates to a buffing composition, and, in particular, to a composition that imparts a very fine finish to automobile surfaces.
2. Discussion of the Art
In the 1980,'s, automobile manufacturers began using a base coat/clear coat paint system for automotive surfaces. The base coat imparts the desired color and the clear coat, which is applied over the base coat, is a transparent, hard, chip-resistant, protective coat. This paint system magnifies painting defects in either the base coat or the clear coat. If the defects cannot be corrected on the assembly line, the automobile must be removed from the line, the defects removed, and the automobile then repainted. This procedure results in a considerable loss of time, and consequently, money for the automobile manufacturer. Minnesota Mining and Manufacturing Company, the assignee of the present application, has developed a system used by automobile manufacturers to remove paint defects on the assembly line. The system, known as the "Finesse-it" system, first utilizes a sanding step, employing very fine coated abrasives, to smooth out the defect. Next, the defect is buffed with "Finesse-it" brand finishing material (a buffing composition) to remove the scratches produced by the coated abrasives. Finally, the residue from the finishing material is removed with a cotton cloth, thereby producing a uniform, glossy finish. An optional step is to polish the surface after buffing to impart an even finer finish to the painted automobile surface. The "Finesse-it" system has had wide-spread success in automobile manufacturing plants, except in the finishing of dark colored paints. The "Finesse-it" finishing material (the buffing composition) tends to leave a faint white "spider-web" scratch or a milky haze on the painted surface where the defect was repaired. It would be desirable to use a buffing composition that does not produce haze marks, so that paint defects can continue to be removed on the assembly line.
In addition, automobile manufacturers require that the buffing compositions contain no silicone-containing materials. When silicone-containing materials are utilized in a buffing composition, a residual layer of silicone is left on the painted surface. When the clear coat is applied to this surface, or if the surface is repainted, the residual silicone prevents the paint from evenly spreading across the surface, thereby resulting in serious defects in the painted surface.
Buffing compositions, or polishing compositions, generally comprise very fine abrasive particles suspended in a liquid medium. For example, U.S. Pat. No. 2,597,871 and British Patent Specification 1,221,739 disclose polishing compositions comprising polyethylene wax and silica.
U.S. Pat. Nos. 2,804,440; 2,949,374; and 4,347 333; and Canadian Patent 929291, disclose buffing compositions comprising a synthetic wax, a silicone compound, and abrasive particles.
In general, silicones are preferred in buffing compositions because they increase the water resistance, increase the gloss, improve the workability of the buffing composition, and lower the surface tension of the buffing composition. However, as discussed previously, automobile manufacturers refuse to employ buffing compositions that contain silicone-containing materials.